Cubic crossover equation of state for mixtures

In a preceding publication [S.B. Kiselev, Fluid Phase Equilibria 147 (1998) 7], a general procedure was proposed for transforming any classical equation of state (EOS) for pure fluids into a crossover EOS which incorporates the scaling laws asymptotically close to the critical point and is transformed into the original classical EOS far from the critical point. In the present paper, we extend this procedure and develop a cubic crossover equation of state for mixtures. A comparison is made with experimental data for pure methane, ethane, CO2, and for the methane+ethane and CO2+ethane mixtures in the one- and two-phase regions. The cubic crossover equation of state yields a satisfactory representation of the thermodynamic properties and the vapor–liquid equilibria of pure fluids and fluid mixtures in a large range of temperatures and densities, including the dilute gas limit, liquid densities, and the critical region.